An endoscopic procedure means searching and screening inside the human body by means of a medical device (the endoscope) at a hollow organ or a cavity of the body for medical purposes. Unlike most other medical imaging devices, endoscopes are inserted directly into the organ, and usually use an optical camera in the visible frequencies, or near visible frequencies (such as infra-red beams) in order to produce images and video frames from within the organ. Usually, the endoscopic procedure comes to test whether there are suspicious local regions in the tested organ, such as polyps, tumor, or evidence of cancerous cells.
A colonoscopy procedure is an endoscopic test of the large bowel (large intestine) and the distal part of the small bowel with an optical camera (usually with a CCD or CMOS camera) on an optic fiber or a flexible tube passed through the anus. It provides a visual diagnosis (e.g. ulceration, polyps) and provides the opportunity for biopsy or removal of suspected colorectal cancer lesions.
The main interest in Colonoscopy for the general public is removal of polyps as small as one millimeter (mm) or less. Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not. It takes 15 years or fewer for a polyp to turn cancerous.
The American Cancer Society “Guidelines for the Early Detection of Cancer” recommends, beginning at age 50, both men and women to undergo Flexible Sigmoidoscopy (minimally invasive examination of the large intestine from the rectum through the last part of the colon) every 5 years and Colonoscopy every 10 years.
A polyp is usually defined as a growth of excess of tissue that can develop into cancer. If a polyp is found, it can be removed by one of several techniques. Regarding shape, polyps are usually categorized into two types: pedunculated (see FIG. 1A), and sessile (see FIG. 1B). A pedunculated polyp looks like a mushroom, and a sessile polyp looks like a bump, or can be even flat on the colon tissue. The polyps can vary in size from a few centimeters, to a few millimeters, and can be even less than 2 mm or 1 mm in size. It is more difficult to detect small polyps (less than 6 mm) than large polyps, sessile are more difficult to detect than pedunculated since they are less salient form the colon tissue. Flat polyps are more difficult to detect than bump polyps, and very small (less than 2 mm) flat polyps are usually the most difficult to detect. It is important to detect even small polyps, since once they are detected, even if not suspicious as cancerous, the physician will ask the patient to come back for repeated examination in about 1 or 2 or 3 years (depending on the type and size of polyp) in order to follow up on those polyps.
The two main common types of polyps are hyperplastic polyps and adenoma polyps. The hyperplastic polyps are not at risk for cancer. The adenoma is thought to be the main cause for most of colon cancer cases, although most adenomas never become cancers. The physician usually cannot detect the type of polyp visually, and therefore the suspicious polyps are usually removed (unless they are very small) and are taken to a histology examination under a microscope. It's impossible to tell which adenomatous polyps will become cancers, but larger polyps are more likely to become cancers and some of the largest ones (those larger than 2.5 cm) can already contain small areas of cancer.
The device used for colonoscopy investigation procedures usually comprises 3 parts: 1) The endoscope which is the unit inserted into the colon (at least its distal part); 2) A control at the proximal part which helps guiding the endoscope in the colon; and a computerized external unit connected to the video output of the endoscope, receiving images and video frames from the colon. The unit usually includes a graphic processor to process and display the best possible images on an attached screen. The computerized unit usually also has additional external video outputs to which the processed video frames are passed in addition to the main video output which is destined for the main screen of the device.
Usually, a colonoscopy test is performed after the colon has been evacuated, usually via a clyster. There are some alternatives procedures such as X-ray Virtual Colonoscopy, in-vivo Ultrasound colonoscopy, in which evacuation is not required.
The colonoscopy procedure is mainly a screening test (a test for detection, preferably early detection, of a disease or a chance to have a disease). While the physician inserts the endoscope into the colon, he/she navigates it to its final destination (the farthest location, from the rectum, in the colon which he/she plans to reach with the distal part of the endoscope). During this navigation the physician looks for suspicious polyps in the colon, and if found, the physician then considers immediate removal of the polyp with a special tool which can be inserted to the colon with the optical endoscope. However, the main search and detection for suspicious polyps is done during the pull-out of the endoscope from the colon, since then the physician can be concentrated in this search without taking care for the navigation process (during the pull-out the endoscope just follow the tubular structure of the colon).
In addition to the challenge of detecting small and flat polyps, or polyps which are similar in texture and color to the regular colon tissue, one of the main difficulties in a regular colonoscopy procedure is the detection of polyps which are hidden behind concealed parts of the colon folds (polyps to which the endoscope camera has no direct line of sight). To overcome this difficulty, several tools started lately to be developed, such as an endoscope with additional cameras looking backwards, endoscopes with cameras which can view to the side or have optics which enables them to look backwards, and special balloon which is added to the endoscope in order to unfold the colon folds in the camera region.
In some back to back tests which were done with regular colonoscopy tests followed by a test of one of these techniques to see also the hidden polyps, it was found that regular colonoscopy tests miss up to 28% of all polyps and up to 24% of the adenoma polyps which are considered more dangerous regarding causes for cancer. These findings enhance the importance of developing tools that would help the physician to locate more suspicious tissues and polyps in the endoscopic screening tests with a higher precision rate and accuracy rate.